     .ORIG x1200
;increment by 1 at addr x4000  
     LEA R5, U
     LDW R5,R5,#0
     LDW R7,R5,#0
     ADD R7,R7,#1
     LEA R5, U
     LDW R5,R5,#0
     STW R7,R5,#0
     RTI

U    .FILL x4000
     .END
